The standard cooling solution for telecommunications equipment (and other heat generating equipment) is to thermally connect metal (e.g., aluminum) heat sinks to heat generating components and to force air through these heat sinks via fans. However, next generation electrical, optical and/or electro-optical products have significantly increased power dissipation due to enhanced functionality, power density and so on.
Increased power density of components requires increased cooling levels, such as provided by improved heat sinks or higher fan airflow.
One improvement in heat sink design is the use of copper instead of aluminum. Copper has twice the thermal conductivity of aluminum, but is much more expensive. Moreover, even pure copper heat sinks do not supply adequate cooling for some equipment, such as remote network controller boards. Copper heat sinks may be augmented by using heat pipes to spread the heat evenly on the base of the heat sink.
Increasing fan-derived airflow in not a comprehensive solution. Fans are a significant source of audible noise, and the operation of fans at higher power or airflow is constrained by allowable noise levels (typically 65 Dba in a central office environment). In addition, fans are relatively unreliable in comparison to other types of components, especially when operated at maximum power and/or at high temperatures.
In the case of optical transport circuit packs, the best solution heretofore recognized was to place individual parallel fin heat sinks on each of the optical transceivers (such as small form-factor pluggable transceivers, SFPs and/or XFPs). Due to the size of the optical transceivers, there is little available space for extra height on the optical transceiver heat sink fins, such that shorter (less effective) optical transceiver heat sinks are typically used. Also, because each optical transceiver has its own individual heat sink, there is wasted space in between each optical transceiver where extra heat transfer surface material could be utilized.